| The collapse is a kind of erosion type in the weathered granite area of southern China,which has a serious negative impact on the local society,ecology and economy.Our country vigorously promotes the construction of ecological civilization,domestic scholars have done a lot of research on collapse erosion,and at the same time accumulated remarkable scientific research results.However,there are relatively few studies on wall collapse erosion and prevention and control of typical granite development,and the characteristics of collapse wall erosion are more remarkable.The poor control effect leads to the expansion of collapse area and the aggravation of soil and water loss.The collapse of the wall is an important part of the collapse,which is easy to occur,and its erosion characteristics are extremely different.The research on the control of collapse erosion is mainly focused on engineering measures,and the research on the control of collapse erosion with jute mulching is less carried out.The soil selected in this experiment is the soil of each layer of collapse wall developed by typical granite in Wuli Village,Tongcheng County,Hubei Province.The indoor artificial rainfall experiments combined with different slopes(5°?15°),different rain intensities(60mm/h?90mm/h)and different jute mulching grid(Blank?3cm×3cm?6cm×6cm)were used to study the variation process of runoff and sediment yield on different soil layers of soil slopes.Distribution characteristics of particles in runoff and sediment and hydraulic mechanism under slope erosion.At the same time,we could reveal the rainfall erosion characteristics of different soil layers of wall collapse,and provide theoretical basis and technical guidance for the prevention and control of collapse.The conclusions of the experiment are as follows:(1)Under the condition of the same rainfall intensity and slope,the runoff yield time of each layer increased with the increase of jute fiber coverage,and the topsoil layer was the largest,while the sand layer and stripe layer were smaller;Taking topsoil as an example,under the condition of rain strength of 60mm/h and gradient of 5°,with the grid density of jute fiber from uncovered to 6cm×6cm grid to 3cm×3cm grid,the runoff generation time is 69s,96s and 101s,respectively.Under the condition of the same slope and mulch,the runoff yield time of each layer decreases with the increase of rain intensity.Taking stripe layer as an example,when the slope is 15°and 6cm×6cm grid jute geotextile is covered,the runoff generation time is shortened by 23 s with the increase of rain intensity.Under the condition of large slope,the rain intensity has little effect on the initial runoff generation time of each level,and under the condition of small slope,the rain intensity has a great influence on the initial runoff generation time of each level.(2)In the process of rainfall,the slope runoff of each layer of soil increases with the increase of rain intensity,and the sediment yield of slope decreases with the increase of jute geotextile coverage.Among them,the sediment yield of topsoil layer is the smallest,and the sediment yield of stripe layer and sand layer is larger,which the fluctuation is obvious.When the rain intensity is 90mm/h,the slope is15°and the jute grid is 3cm×3cm,the sediment yield of the four soil layers is as follows:The topsoil layer is593g/min·m~2-153g/min·m~2,the red layer is 433g/min·m~2-205g/min·m~2,the stripe layer is383g/min·m~2-218g/min·m~2,and the sand layer is 983g/min·m~2-521g/min·m~2;With the increase of rain intensity and slope,the sediment yield of stripe layer and sand layer varies greatly with time.Under the combined action of rain intensity,slope and coverage,the sediment yield of the four soil layers increased at first and then decreased and tended to be stable with the rainfall.There was a significant negative correlation between sediment yield and jute geotextile coverage,in which the topsoil layer was 0.595,the red soil layer was 0.720 and jute geotextile could increase the soil holding capacity of slope soil.From the point of view of the control effect of jute geotextile,it has the greatest effect on soil and water conservation in topsoil layer,but little effect on soil protection in sand layer and stripe layer.(3)Through the distribution of sediment particles produced by rainfall runoff on different levels of soil slope,it can be seen that,taking sand layer as an example,under the treatment of rain intensity 90mm/h,slope 15°,3cm×3cm grid jute treatment,the content of sand and powder in the runoff sediment particles is 22-50%?31-77%,The clay content is 12%-23%,and the gravel content is the least.When the rain intensity and slope are constant,with the increase of jute geotextile coverage,the content of large particles in runoff sediment decreases and the content of small particles increases.Under the condition of 90mm/h rain intensity and 15°slope,the effect of jute geotextile on sediment storage of each grain diameter is weak.In terms of the distribution of sediment particles in runoff with time,under the condition of the same jute geotextile mulching,rain intensity and slope,the sand content decreased at first and then tended to be stable and at a lower level.As far as the particle size distribution of sediment on different soil layers is concerned,jute geotextile mulching has better interception effect on soil large particles on topsoil layer and red soil layer slope,weak interception effect on small particles,and less effect on soil and water conservation on sand layer and stripe layer slope.(4)Among the hydraulics characteristics of slope erosion,the flow velocity on the slope is the smallest at the top of the slope,which increases with the increase of slope length,and slows down at the bottom of the slope.The flow velocity of the slope under jute geotextile mulching is lower than that without jute fiber mulching,and decreases with the increase of jute geotextile coverage.Among them,the flow velocity of the topsoil layer is about 0.035m/s and the sand layer is about 0.072m/s under the rain intensity of 60mm/h,the slope of 5°and the jute of 6cm×6cm.The resistance coefficient of each grade increases with the increase of coverage and decreases with the increase of rain intensity and slope.The Froude number of slopes decreases with the increase of coverage,and the slope and the roughness of soil surface are the main reasons that affect the flow pattern.(5)When rainfall and slope are constant,the sediment yield of soil slope is positively correlated with the flow velocity and the Froude number,and negatively correlated with the resistance coefficient.At the same time,the coverage of the jute geotextile at all levels is negatively related to the flow rate of water and the number of Froude,the correlation between topsoil layer and red soil layer is more significant than that of sand layer and stripe layer.There was a significant positive correlation between jute geotextile mulching and resistance coefficient.The sediment yield on the slope is closely related to jute fiber coverage,velocity and Froude number.Jute geotextile mulching can effectively intercept slope runoff and sediment,reduce slope flow velocity and increase soil surface roughness. |
PDF Full Text Request